Now that you have begun to learn about organelles, it is time to
make sure that you understand how we see these things! Because, if you are like me,
it is hard to understand what something is or does without knowing what it looks like.
Or how big it is. Or how to see it.

People really didn't know anything about most of the organelles
until the 1950s. And they didn't really make much sense out of it all until the
1960s. So, the study of cell biology didn't really blossom until recently. The
specific thing that brought about the explosion our understanding of cells was the
electron microscope. You see, most of the organelles that you are learning about are
invisible using even the nicest light microscopes. And you will certainly not see
these items in your microscopes at home (or in a $100,000 light microscope in a government
lab).

Your book describes electron microscopes a little bit for you.
Go ahead and read about them. I'll also tell you a little bit about them
here. Please keep in mind that the information on this page is only here to help
you... I will NOT be testing you on how light or microscopes specifically work, but I want
to show you. It really helps to understand things that are so tiny.

Regular light microscopes, like the ones you have purchased, use
light to help you see an item. That should make sense, because our eyes only
see when there is light around. If light does not go through something or bounce off
of something, we don't see anything. In this drawing I made, I have tried to show
this to you... when you look at another person, light is reflected off of them and then
you see it when that reflected light reaches your eye. When you look in your
microscope, the light passes through the material of interest on your slide and then up
through the ocular to your eye. Either way, the light carries some of the
information about what you are seeing, and then your eye can recognize that information.

This alone is pretty impressive. And to understand it a little
better, it helps to know that light travels in waves.

Light seems so small to us. We can't see the little light
waves. But then again, cells are too small for us to see, too. At some point,
as we try to see things that are smaller and smaller and smaller, we will have to get so
small that we reach the size of light.

Light waves are really small. They are around 1 - 2
micrometers in size. That is 1 - 2 thousandths of a millimeter. And the
eukaryotic cells we are studying are around 10 - 30 micrometers in diameter. So
light is small enough to show us these eukaryotic cells. But, the parts that make up
the cell have to be much smaller than the cell itself. It is most of these parts
that we cannot see with the microscope. Here's why.

At the top of this picture I have drawn light reflecting
off a person. This is to show you that a person is big enough to reflect and change
light.

In the middle, I have drawn a picture of light going through a
eukaryotic cell... This is like the situation that you create when you look at cells under
your microscope. The light comes from below the stage as normal white light, and
then runs through your specimen, and changes (in this case, it changed color) as a result.
You can see the cell because it was at least as large as the light wave.

At the bottom, I have drawn a small organelle. This
is something like a ribosome or lysosome, which are typically less than 1 micrometer in
size. It could be the ER, which is less than 1 micrometer in diameter,
even if it is extensive. Note that this item is smaller than the light wave. The light wave
doesn't even notice it and runs right past it without changing.

So, if an organelle is around 1 micrometer in size or larger, the
light will change from it and you will see it. If it is smaller than that, the light
will not be affected by it and you will not see it.

Electron microscopes do not use light

Electron microscopes run an electron beam through the tissue you are
interested in. Electron waves are much smaller than light waves. They can pick
up things in the nanometer range (1000 nm = 1 micrometer). Of course, we can't see
the electron beam, so we need special equipment to help us see our images. Electron
microscopes are quite finicky and expensive and difficult to use-- that's why most schools
(including STCC) do not own one.

I hope you can understand, though, after this little tirade of mine,
why we learned so much after the electron microscope was developed. We had never
seen the rER or the Golgi complex or the lysosome before the electron microscope.
Once we could see them, then we could figure out what they did and why they were
important. As you look around the WWW at images of cellular organelles, you will
encounter many that were taken with the electron microscope. Most of these appear in
grayscale, although some people like to colorize them to make them prettier.